The invention to which this application relates is to apparatus for use in the application of a coating, typically by sputtering of material from one or a series of targets provided as part of respective magnetrons.
The invention also relates to the provision of improved coatings which are corrosion resistant and therefore allow the protection of articles which otherwise would be prone to corrosion in their normal environmental conditions.
The application of material onto articles to form a coating layer or layers using the sputtering of material from targets located with magnetrons is well known. There are several different forms of apparatus which can be used, one of which is referred to as a closed field unbalanced magnetron array with the magnetrons being provided in a spaced array within a coating chamber which is held in a vacuum. The articles to be coated are selectively placed in the coating chamber and may be moved so as to allow the exposure of the articles to the sputtered material from the targets. The selective activation of the targets and/or selective introduction of gases into the coating chamber, allow the particular form of layers and the formation of the layers to be adjusted and hence the coating to be formed in a desired manner.
A known problem with magnetron sputtering apparatus is that the deposition rates can be relatively slow in comparison to other coating forming means. This has therefore tended to mean that while the quality of the coatings which are applied are of a standard so as to make the same attractive for relatively high cost articles, the coating of lower cost articles using the magnetron sputtering method and apparatus may not always be commercially practical. This therefore means that articles may be coated by other deposition methods which have a higher deposition rate but frequently, the coatings are of inferior quality. One such type of article is a plate for a fuel cell, typically for use in automobile or other vehicle power systems. The fuel cell plates are used in liquid which is corrosive and therefore the fuel cell plates need to be protected from corrosion. Conventionally this is achieved by coating the fuel cell plates with an inert metal such as precious metal such as gold or platinum. These materials are expensive. It is also important that the coating which is applied is conductive in this particular use and indeed in many other uses there is a desire to be able to provide a conductive, corrosion resistant coating.